Nuclear spin-lattice relaxation times have been measured using acoustical techniques. These techniques involve the measurement of transient effects in nuclear acoustic resonance. Two methods have been used: progressive saturation, in which the resonance line is repetitively scanned in a time short compared to the relaxation time, and, saturation and recovery, in which the resonance line is first saturated strongly and then observed a variable time later. These methods have been applied to an aluminum alloy, for which the coupling to the nucleus involves the magnetic dipole moment, and tantalum, for which the coupling involves the electric quadrupole moment.

Theoretical expressions are derived for the signal-to-noise ratios in magnetic resonance experiments for the lock-in and multiple-scan direct detection schemes. Effects of noise character, post-spectrometer filters, and modulation frequency are included in the analysis. The theoretical results are found to be in good agreement with experiment for the specific case of nuclear acoustic resonance in a metal single crystal.

5 uclear acoustic resonance has been investigated in single-crystal aluminum over a broad range of acoustic power. Saturation of both absorption and dispersion signals was observed. The shape and width of the absorption signal were found to depend on the acoustic power le~el.The line was found to either narro~or broaden with increasing acoustic power, depending on the magnitude of the low-frequency modulation field. The linewidth and shape changes were accounted for by the theory of Provotorov as expanded by Goldman, and Revokatov, and Lyapukhov. The signal intensity was found to decrease rapidly at high acoustic-power levels. This decrease is not accounted for by the above theories.

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A rotatable sample holder suitable for use at low temperatures is described. This holder was designed for continuous wave ultrasonic experiments. The rotation mechanism and the angle sensing mechanism are discussed.